RF power transistor devices are generally known for use as signal amplifiers in wireless communication applications. As demand for wireless communication applications has increased, the operating frequency for wireless networks has also increased. Operating frequencies are now well into the gigahertz range.
Natural variables in individual transistor elements have made mass production of RF power transistors problematic. Transistor devices naturally vary as to input capacitance, gain and phase shift. Particular transistor devices are preliminarily characterized over a range of expected operating frequencies and voltages. Further devices are then made using like materials in an attempt to make these devices operate within the characterized ranges. Due to the variations in transistors and various other elements over identical operating frequencies and voltages, however, the ability to successfully tune transistor devices on a large scale manufacturing basis is limited.
RF power transistor devices generally have a plurality of electrodes formed on a silicon die, each electrode having a plurality of interdigitated transistors. The individual transistors of each electrode are connected to respective common input (gate) and output (drain) leads for each electrode. As is known, the die is generally attached by a eutectic die attach process atop a metallic (source) substrate. The substrate is mounted to a metal flange, which serves as both a heat sink and a ground reference. The input (gate) and output (drain) lead frames are attached to the sides of the flange. The lead frames are electrically isolated from the metal (source) substrate and are coupled to the electrode input and output terminals, respectively, on the silicon die by multiple wires (i.e., bonded to the respective terminals and lead frames).
At high operating frequencies, it is particularly important that the input and output electrode terminals be impedance matched to the desired operating frequency ranges. In lower frequency (i.e.:<1 GHz) high power applications, the required inductances of shunt matching elements can cause the wires to be to long and few to handle the operating power. In some cases previous methodologies to solve this have lead to solutions with excessive cross talk between the input and output networks, causing instabilities.
Examples of RF power transistor devices available in the prior art are illustrated in U.S. Pat. No. 6,177,834 and U.S. Pat. No. 6,614,308, incorporated herein by reference.